Segment Information - Goodwill and Total Assets (Details) - USD ($) $ in Thousands	Jun. 28, 2015	Dec. 31, 2014	Jun. 29, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Goodwill	$ 167,936	$ 170,773	$ 184,994	$ 136,152
Total Assets	1,400,403	1,417,818
Industry [Member]
Segment Reporting Information [Line Items]
Goodwill	78,695	76,858
Total Assets	472,350	444,168
Science [Member]
Segment Reporting Information [Line Items]
Goodwill	89,241	93,915
Total Assets	407,726	470,899
Corporate Eliminations [Member]
Segment Reporting Information [Line Items]
Total Assets	$ 520,327	$ 502,751